South America's most famous lake is being polluted by increasing levels of waste from fast-growing cities, according to locals, environmentalists and politicians.
Lake Titicaca, which sits on the border of Bolivia and Peru, has sustained agricultural societies on the dry, high-altitude Andean plains for thousands of years, but is now threatened by a population boom from nearby cities and towns.
El Alto has grown at 4 percent a year for two decades as rural peasants seek a better life, and is now the country's second largest city and the largest urban centre in the Titicaca watershed.
But this migration has had devastating effects on the rivers of El Alto, communities downstream and Lake Titicaca. Raw sewage, garbage and industrial waste are all dumped into the Seco River, which flows through the heart of El Alto. At the edge of the city, where the Seco begins a 40-mile journey toward Lake Titicaca, it also receives treated wastewater from the city's severely overtaxed treatment plant. Those waters mix and travel out over the flat plains.